The present invention relates to a technique for preventing the occurrence of an event in which the data pre-recorded on the data tracks of a magnetic disk drive is lost by data writing onto data tracks adjacent to the foregoing tracks.
The magnetic disk of a magnetic disk drive that is a recording medium has multiple data tracks set by servo data concentrically on the recording faces of the disk, and multiple data sectors (hereinafter, referred to simply as sectors) are set in a circumferential direction on each data track. The sectors become the minimum unit of the data recorded on the magnetic disk, and are set as, for example, 512-byte storage blocks. Each data track is arranged on the magnetic disk in a radial direction thereof at a required track pitch, and the magnetic disk drive, after receiving a command from a host apparatus, positions an associated magnetic head at the data track including the sectors of a specified address.
In recent years, with the improvement of magnetic disks in recording density, track pitch density (the number of tracks per inch, TPI) has become increasingly small. Accordingly, the event that since magnetic flux leakage from a write head during data recording on a data track affects the data pre-recorded on adjacent data tracks, an increase in the updating frequency of the data recorded on that track eventuates in the pre-recorded data being lost or becoming unreadable, is occurring in the magnetic disk drives used for specific purposes. This event is known as adjacent-track interference (ATI). Patent Document 1 (Japanese Patent Laid-Open No. 2004-273060) discloses a technique in which, as summarized in the “Abstract” thereof, even if the situation arises that leakage fields progressively erase data present on adjacent data tracks, this situation is compensated for to prevent a data error from occurring in the magnetic disk drive.
The technique described in Patent Document 1 employs the steps of counting the number of writing operations on a data track, detecting that the writing operations count has reached a predefined value, temporarily reading the data on data tracks adjacent to that data track, and rewriting data onto the adjacent data tracks. Also, when data is written onto data tracks, writing of the data skips alternate physical data tracks, and completion of writing onto half of all data tracks is followed by writing onto the skipped data tracks.
Patent Document 2 (Japanese Patent Laid-Open No. Hei 3-203071) discloses a technique in which, since a magnetic disk, because of its circumferential velocity, is smaller in TPI margin at its outer data track than at its inner data tracks, the TPI margin is made constant over the entire magnetic disk surface. More specifically, in order to ensure higher recording density, servo signals are written so that the data track pitch continuously changes to be wider as the data tracks are more distant from the inner edge of the magnetic disk.